According to West Seattle Blog, it’s a bloom of microorganisims called noctiluca, read more here.  

Our intredeped reporter, Scupper, decided to check out the scene and is sharing these photos and video.

We're not sure "why" but it appears that this Coast Guard gunboat is following this sailboat.

The Rochade flies the Caman Island flag and is a creation from Delta Marine that's out for a test drive in Puget Sound.  

Here's a little more we found:

She can sleep up to twelve guests in five cabins and up to ten crew members in five crew cabins. Rochade is classed to Lloyd's Register and compliant to the MCA. 

On the technical side, Rochade uses twin MTU V16 4000 diesel engines. 22 knots is the expected top speed with a cruising speed of 18 knots. At 12 knots, a healthy range of 2,700 nautical miles is expected, drawing from 53,000 LT tanks. This new Delta is up for sale through a reputable broker.

Delta Marine is the builder of the yacht Laurel, which we wrote about a few years ago when she too was off the shores of West Seattle.

I'm not sure which one this is…I'm not seeing this vessel (#7) on www.marinetraffic.com.